Treating the human bladder with capsaicin: Is it safe?

Objectives: Although human contact with capsaicin has occurred over thousands of years, some uncertainty surrounds its status as a possible carcinogen. This is the first report of bladder biopsies from patients who have been treated with capsaicin over a 5-year period. Methods: Between 1991 and 1996, 20 patients (9 males, 11 females; mean age 52.5 years, range 40-70 years) with intractable detrusor hyperreflexia have had repeated instillations of intravesical capsaicin (1-2 mmol/l). The number of treatments per patient varied between 1 and 17 (total = 82; average 6/patient). The surveillance programme involved repeated flexible cystoscopy and bladder biopsies before and after capsaicin. Cryostat sections were stained with haematoxylin-eosin and examined by light microscopy. Results: None of the bladder biopsies have shown metaplasia, dysplasia, flat carcinoma in situ, papillary or solid invasive cancer. Conclusions: No pre-malignant of malignant change has been found in biopsies of patients who had repeated capsaicin instillations for up to 5 years. However, as the morphological effects of chemical carcinogens may not be apparent for 10 years, further surveillance is being continued.